Organohalosilanes, halosilanes, and in particular methylchlorosilanes, are the building blocks from which silicone polymers are produced. Organohalosilanes and halosilanes are commercially produced by what is commonly called “the direct process”, in which silicon metal is reacted with an organic halide or hydrogen chloride, optionally in the presence of a catalyst. The direct process is well known in the art, and is well described in patent literature.
In, for example, the commercial production of methylchlorosilanes by the direct process, finely ground silicon metal powder is reacted with methyl chloride in the presence of a catalyst by fluidising the silicon powder in a fluid bed by passing methyl chloride gas there through at a temperature of between 200° C. and 500° C. A by-product of the direct process is direct process residue (DPR). DPR comprises the higher boiling point halosilanes produced by the direct process. DPR is a chemically active, hazardous material, whose reactivity must be reduced prior to transportation and/or disposal. Thus, once separated from the other reaction products, DPR is neutralised, for example, with lime solution, to reduce its activity, and dewatered, resulting in a gel-solids mixture, referred to hereinafter as “DPR gel”. Methods for neutralising DPR are well known in the art, see for example U.S. Pat. No. 4,408,030 (Dow Corning), U.S. Pat. No. 4,690,810 (Union Carbide) and U.S. Pat. No. 5,876,609 (General Electric).
DPR gel is presently a cost creating waste material. The present inventors have now found a useful way of utilising DPR gel in which the DPR gel is used as an additive in pre-ceramic mixtures. The resulting ceramic articles typically demonstrate improved physical and/or physicochemical properties.